If you ask at a signage company they will give you a scrap of 4.5mm thick "opal" acrylic for free I would bet. Its pretty hard to beat. And yes, you definitely need it to hide the light source from showing in your image.

I hate analog circuits! I can't believe I picked a project that would need me to deal with analog.

I think I need to reverse my video signal + / - on the OP-AMP. I think anything getting near 0 volts is triggering the comparator. I have to turn my pot all the way to the right to get the signal to trigger. In reality, I shouldn't even need a pot if the signal was inverted. Just like a 1k or so resistor should be enough to say the inverted voltage went above 0 volts. When I first put the circuit together I thought it would need to be inverted but since it was working I went with it.

Tonight I put together my lightbox and wired up my white LEDs in 2 sets of three in series. Using a 24ohm resistor on each set. I applied 12v slowly. I was afraid my bench power supply was going to destroy the LEDs but, they survived. They claim to be 13000mcd and they are very bright. After going down the 75mm box through the 3 pieces of Parchment baking paper I am satisfied with the diffusion. However, I am not so convinced the output will be bright enough.

i always used 2 or 3 layers of milk bottle plastic that worked for me used it in fact on the 2 drum monitor builds..the type of plastic used will defocus the leds.

The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.

The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.

FlyMario wrote:That a milk jug that you used as the diffuser? Recycling!

Yes pretty much those squareish ones trying to cut out the 4 flat panels for fitting in the drum.. don't think i bothered with the side with the sticker to get that off up higher

The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.

Here is the readings from the Arduino. The first column is the speed of the PWM out for the motor, second column RPM frame time and the third is the Frame time from the Sync Pulses. I am very happy as I have cleaned up the Sync pulses from the video in.

I had replaced my RPM indicator with one of these modules. Oh these are such crap. No matter what I did I could not get a solid signal.

So I went back to using my OP Amp circuit (common from the google machine) and am so very pleased. Solid.

Your problem with the Chinese-made module maybe one or both of two things. First, depending on the distance from the disc to the LED and detector, they may need angling in towards each other for better coverage and sensitivity - looking at the photo that may be difficult to achieve. A lot of these devices have a beam-width/sensitivity curve of only some +/-10 degrees.

Second is if the disc markings for this are printed (laser or ink-jet) rather than 'done in hardware' a lot of inks (black in this case I assume) are reflective at IR.

Steve Anderson wrote:Your problem with the Chinese-made module maybe one or both of two things. First, depending on the distance from the disc to the LED and detector, they may need angling in towards each other for better coverage and sensitivity - looking at the photo that may be difficult to achieve. A lot of these devices have a beam-width/sensitivity curve of only some +/-10 degrees.

Second is if the disc markings for this are printed (laser or ink-jet) rather than 'done in hardware' a lot of inks (black in this case I assume) are reflective at IR.

I hope this helps...

Steve A.

Yeah, honestly I went down that route because for some reason I could not figure out why a simple OP-AMP and IR Receiver Diode would not work as it had for me before. You see, I had put the output into an Arduino chip. I had failed to program the chip to have that pin be an input... in fact, I had not programmed it at all and just relied on a led to indicate the mark had passed. The Arduino chip was messing with my results. So I decided to use that module.

When I tried the little module it seemed to show promise and I began programming the Arduino chip and monitoring the time between the mark passing. After determining the module could not really give me the results I was looking for, I plugged back in my IR Led's and my original mistake slapped me in the face. That original circuit worked! LOL. It was the Atmega328 chip and my rush to put it in the circuit without even programming it causing me a weeks worth of grief. It works perfectly now.

I have way too many hobbies and have much more determination than skill.

Thanks for your comment, Steve. The module was so sensitive to any light. I even had it set so close to the disk at one time it would hit here and there. It would still get pulses on an extremely low setting. It was designed for line following robots. Its sensitivity would make it totally useless for that thus making a bunch of kids very sad.